Of all of the weapons in Rambo's armory the bow has always been seen as the most fictional of his weapon, but it's not.
The 'military bow' was really used by SOG soldiers during their missions, and the one you see in the movies is qute similar to the real one used in Vietnam.
We have already explained that when a team was located over the border, it usually also meant being captured or killed. However, sometimes engaging the enemy was necessary to accomplish the mission. In the jungle the vegetation is thick and if the mission forced the team to strike first it was possible that to get a line of sight on the enemy, SOG soldiers had to get as close to the enemy as just to ten feet away. During the sixties, silenced (suppressed) weapons were already available, but real world silenced weapons are much louder than movies use to show.
At short distances, the bow is more difficult to aim, but much more silent.
So, when SOG soldiers had to get really close to their enemies, they used a compound bow, just like Rambo does.
The only difference between the one used in the movies and the real one is that the real one was collapsible, while the one used in Rambo II needs a wrench to be prepared to shoot.
The explosive arrows, on the contrary, are entirely fictional: they were never used in Vietnam or after the war.
Even in this case we can't talk about pure fantasy, because in theory they can be built using C4 explosives, which is exactly the kind of explosive Rambo screenwriters had in mind when they created them for the second movie plot.
The confirm it's C4 is the ticking we hear before Rambo shoots them: it's a not-so-spectacular detail, but that makes the scene much more believable.
In fact, the C4 explosive can't explode on impact, but it needs an electrical input in order to detonate, so the ticking we hear in the movie is probably a secondary device made to make the arrow detonate even if it strikes a target too soft to trigger the main primer.
Whatever way the timer works, the bow's quietness makes it impossible to locate the shooter.
This is something most Rambo II viewers don't understand and so it created many misunderstandings with the public at large. How is it possible that a whole army responds to Rambo's fire without ever hitting him? The reason is that when Rambo shoots his explosive arrows, he is hidden in the jungle. This, together with bow quietness, makes him completely impossible to find.
So it surely is an exaggerated scene, but the presence of so many believable details is quite rare in the action genre.